JPH05251590A - Semiconductor device - Google Patents

Abstract

PURPOSE:To acquire highly reliable humidity resistance which is hard to be acquired by only reducing ionic impurities by a conventional method by constituting a sealing resin layer for sealing a semiconductor element of a thermosetting resin composition curing body having specified characteristics. CONSTITUTION:A semiconductor device is sealed by a sealing resin layer which consists of a thermosetting resin composition curing body whose volume resistivity is 5X10<11>OMEGA.cm or more at a temperature of 200 deg.C or 2X10<10>OMEGA.cm or more at a temperature of 250 deg.C, ion mobility is 1X10<-8>cm<2>/V.s or less at a temperature of 250 deg.C and ionic impurity content of extracted water at 160 deg.C for 20 hours is 100ppm or less. Thereby, characteristics appreciated by a pressure cooker test, etc., are improved and a long life is realized. Highly reliable humidity resistance which is hard to be acquired by only reducing ionic impurities in a conventional method can be acquired in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device excellent in reliability, particularly in heat resistance and humidity resistance.

[0002]

2. Description of the Related Art Semiconductor elements such as transistors, ICs, and LSIs have conventionally been sealed with ceramic packages or the like to be semiconductor devices, but recently, from the viewpoint of cost and mass productivity, plastic packages have been used. Resin encapsulation, which was previously used, has become mainstream. Epoxy resin has been used for this type of resin encapsulation and has achieved good results. However, due to technological innovation in the semiconductor field, device sizes are becoming larger, wiring is becoming finer, and packages are becoming smaller and thinner, as well as higher integration. Higher reliability (moisture resistance reliability, heat resistance reliability, etc. of the obtained semiconductor device)
Is required to be improved. Particularly, a cured epoxy resin used for semiconductor encapsulation contains an epoxy resin, a phenol resin as a curing agent, and a curing accelerator that accelerates the reaction of the two as main components. Ionic impurities are generated in the process. These ionic impurities are free to exist in the cured resin body and easily move at high temperatures, which significantly deteriorates the electrical characteristics (especially electrical insulation) and moisture resistance of the cured resin body. Since the reliability is lowered, the improvement is desired.

[0003]

Thus, a large amount of ionic impurities are present in the cured resin for sealing, which lowers the volume resistivity, resulting in electrical characteristics and moisture resistance. Is inferior and, for example, a problem occurs that the aluminum wiring is corroded. The volume resistivity (ρ) is
It is represented by ρ = 1 / enμ (e is an elementary charge) from the impurity ion density (n) in the resin cured product and the ion mobility (μ) of the resin cured product. Then, in order not to reduce the volume resistivity ρ, it is necessary to reduce the ion mobility in the cured resin from the above calculation formula. Conventionally, efforts have been made only on how to reduce the ionic impurities in the cured resin, and reliability has been secured by reducing the ionic impurities, but this reduction of ionic impurities is at the limit. As it approaches, further reduction is becoming very difficult. Therefore, in reality, it is difficult to obtain higher moisture resistance reliability and the like only by reducing ionic impurities.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor device having excellent moisture resistance reliability.

[0005]

To achieve the above object, a semiconductor device of the present invention comprises a semiconductor element and a sealing resin layer for sealing the semiconductor element, wherein the sealing resin layer is: It is configured by a thermosetting resin composition cured product having characteristics (A) to (C). (A) The thermosetting resin composition cured product has a volume resistivity of 5 × 10 ¹¹ Ω · cm or more at a temperature of 200 ° C. or a temperature of 250 ° C.
2 × 10 ¹⁰ Ω · cm or more. (B) The ion mobility of the thermosetting resin composition cured product is 1 × 10 ⁻⁸ cm ² / V · s or less at a temperature of 250 ° C. (C) The ionic impurity content of the extracted water of the thermosetting resin composition cured product at 160 ° C. for 20 hours is 100 ppm
Less than.

[0006]

That is, the present inventors have conducted a series of studies to improve the moisture resistance reliability of the cured resin for semiconductor encapsulation. Then, not the ionic impurity content in the conventional resin cured body but the electrical characteristics (volume resistivity, ion mobility, etc.) of the resin cured body used for the sealing resin, and the moisture resistance of the semiconductor device will be examined. Was examined. In the course of research on this electrical characteristic, humidity resistance reliability [pressure cooker bias test (PCBT test)
It has been found that the disconnection due to corrosion of the aluminum wiring in 1.) is correlated with the volume resistivity of the cured resin at 200 ° C. or 250 ° C., and the decrease in volume resistivity is caused by an increase in ion mobility. As a result of further research, the volume resistivity was 5 × 10 ¹¹ Ω · cm at 200 ° C.
Or above 2 × 10 ¹⁰ Ω · cm at 250 ° C,
Ion mobility is 1 × 10 ^-8 cm ² / V at a temperature of 250 ° C
It has been found that excellent moisture resistance reliability can be obtained by using a cured resin of s or less, and when the cured resin has an ionic impurity content of 100 ppm or less at 160 ° C. for 20 hours. Reached

Next, the present invention will be described in detail.

In the semiconductor device of the present invention, the semiconductor element is resin-sealed with a special thermosetting resin composition cured body which is a sealing resin layer.

The above-mentioned cured product of the special thermosetting resin composition is
The components and manufacturing method are not particularly limited, but they can be obtained, for example, by curing an epoxy resin composition that is generally used as a semiconductor sealing resin.

The above-mentioned epoxy resin composition is obtained by using an epoxy resin, a curing agent, and an inorganic filler, and is usually in the form of powder or tablets formed by tableting.

The epoxy resin is not particularly limited, and various epoxy resins conventionally used as a sealing resin for semiconductor devices, such as cresol novolac type, phenol novolac type and bisphenol A type, can be mentioned. The novolac type epoxy resin usually has an epoxy equivalent of 160 to 250 g / eq and a softening point of 50.
The thing of -130 degreeC is used. Furthermore, in such an epoxy resin, the chlorine ion concentration of the extracted water is 1.0
It is preferable to use the one of about 6.0 ppm. The above chlorine ion concentration can be obtained, for example, by extracting the epoxy resin in pure water and measuring the chlorine ion content of the extracted water by ion chromatography.

Preferable examples of the curing agent include phenolic resins such as phenol novolac and cresol novolac. Particularly, the hydroxyl equivalent is 70 to 280 g / eq,
It is preferable to use one having a softening point of 50 to 120 ° C.
Further, among the phenol resins, those having the structural formula shown below can be used. And, in such a phenol resin, it is preferable to use one having a chlorine ion concentration of 0.05 to 0.3 ppm in the extracted water.

[0013]

[Chemical 1]

[0014]

[Chemical 2]

The mixing ratio of the epoxy resin and the curing agent is preferably set so that the hydroxyl group in the curing agent is 0.8 to 1.2 equivalents relative to 1 equivalent of the epoxy groups in the epoxy resin.

Examples of the above-mentioned inorganic filler include silica powder and the like.

In addition to the above components, a silicone compound, a curing accelerator, a flame retardant, a pigment such as carbon black, a release agent and a silane coupling agent may be appropriately added to the epoxy resin composition. can do.

Examples of the curing accelerator include imidazole compounds such as 2-methylimidazole, amine compounds, phosphorus compounds, boron compounds and phosphorus-boron compounds.

The epoxy resin composition is obtained, for example, as follows. That is, the above components are blended in a predetermined ratio. Then, these mixtures are melt-kneaded in a kneading machine such as a mixing roll machine in a heated state, cooled to room temperature, then crushed by a known means, and tableted as necessary to obtain a series of steps. An epoxy resin composition is obtained.

The encapsulation of the semiconductor element using such an epoxy resin composition is not particularly limited and can be carried out by a known molding method such as ordinary transfer molding.

The cured thermosetting resin composition, which is the sealing resin layer of the semiconductor device thus obtained, must have the following characteristics (A) to (C). (A) The thermosetting resin composition cured product has a volume resistivity of 5 × 10 ¹¹ Ω · cm or more at a temperature of 200 ° C. or a temperature of 250 ° C.
2 × 10 ¹⁰ Ω · cm or more. (B) The ion mobility of the thermosetting resin composition cured product is 1 × 10 ⁻⁸ cm ² / V · s or less at a temperature of 250 ° C. (C) The ionic impurity content of the extracted water of the thermosetting resin composition cured product at 160 ° C. for 20 hours is 100 ppm
Less than.

That is, since the semiconductor device of the present invention is sealed by the sealing resin layer made of the thermosetting resin composition cured product having the above characteristics (A) to (C),
The characteristics evaluated by the moisture resistance reliability test such as the BT test are improved and the life is extended.

The volume resistivity of the characteristic (A) is a resistivity specific to a cured product of the thermosetting resin composition, and depends on the temperature thereof. The volume resistivity is obtained by measuring the value of the current flowing through the sample when a voltage is applied to the sample at a predetermined temperature. As this current value, a value one minute after the voltage application is generally adopted.

The ion mobility of the characteristic (B) also has temperature dependency, and the mobility is small, so that it can be measured at high temperature. Various methods have been proposed for measuring the ion mobility, and the method is not particularly limited. However, in the present invention, the polarity reversal method [Tatsuji Nakajima; Electrical Testing Laboratory Journal, 24,
801 (1960)] was adopted. Ion mobility by the polarity reversal method, voltage is applied to the sample at a predetermined temperature,
After a lapse of a predetermined time, the polarity of the applied voltage is reversed and the current is measured. At this time, a peak appears in the current-time characteristic, and the time from when the polarity is inverted to when this peak appears is calculated and calculated from the following formula.

Ion mobility (μ) = d ² / tV [In the above formula, d is the thickness of the sample, t is the time when the polarity is reversed and the current peak appears, and V is the applied voltage. ]

The ionic impurity content of the characteristic (C) is 16 in pure water in a crushed thermosetting resin composition cured product.
It is determined by performing extraction at 0 ° C. for 20 hours and measuring the content of ionic impurities (Na ⁺ , Cl ⁻ , Br ⁻ , SO ₄ ²⁻ ) in this extracted water by ion chromatography.

[0027]

As described above, in the semiconductor device of the present invention, the encapsulating resin layer for encapsulating the semiconductor element has the thermosetting resin composition having the special characteristics (A) to (C) as described above. It is composed of a cured product. Therefore, the characteristics evaluated by the pressure cooker test (PCT test) or the like are improved and the life is extended. Therefore, it has high moisture resistance reliability that was difficult to obtain only by reducing conventional ionic impurities.

Next, examples will be described together with comparative examples.

First, prior to the examples, the following epoxy resins a to f, phenol resins g and h, and curing catalysts i to k were prepared. In addition, the chlorine ion concentration in the following epoxy resin and phenol resin is 160 in pure water.
The extraction was performed at 20 ° C. for 20 hours, and the content of chlorion in the extracted water was measured by ion chromatography.

[Epoxy resin a]

[Chemical 3] Epoxy equivalent: 221 g / eq, softening point 97 ° C, extracted water chlorion concentration: 1.54 ppm

[Epoxy resin b]

[Chemical 4] Epoxy equivalent: 233 g / eq, softening point 83 ° C, extracted water chlorion concentration: 4.44 ppm

[Epoxy resin c]

[Chemical 5] Epoxy equivalent: 250 g / eq, softening point 81 ° C., number of repetitions n = 0-2, extracted water chlorion concentration: 1.01 p
pm

[Epoxy resin d]

[Chemical 6] Epoxy equivalent: 250 g / eq, softening point 92 ° C., number of repetitions n = 0-2, extracted water chlorion concentration: 1.81 p
pm

[Epoxy resin e]

[Chemical 7] Epoxy equivalent: 195 g / eq, softening point 107 ° C., repetition number n = 0 to 1, extraction water chlorion concentration: 5.64
ppm

[Epoxy resin f]

[Chemical 8] Epoxy equivalent: 195 g / eq, softening point 69 ° C., number of repetitions n = 1 to 4, chlorion concentration in extracted water: 5.18 p
pm

[Phenolic resin g]

[Chemical 9] Hydroxyl equivalent: 176 g / eq, softening point 76 ° C., number of repetitions n = 0 to 3, extracted water chlorine ion concentration: 0.075 p
pm

[Phenolic resin h]

[Chemical 10] Hydroxyl equivalent: 107 g / eq, softening point 67 ° C., number of repetitions n = 1 to 6, extracted water chlorion concentration: 0.261 p
pm

[Curing catalyst i]

[Chemical 11]

[Curing catalyst j]

[Chemical 12]

[Curing catalyst k]

[Chemical 13]

[Curing catalyst 1]

[Chemical 14]

[0042]

Examples 1 to 7 and Comparative Examples 1 to 3 The components shown in Tables 1 and 2 below were blended in the proportions shown in the same table, melt-kneaded for 3 minutes with a mixing roll machine (temperature 100 ° C.), and cooled. After solidification, it was pulverized to obtain the desired powdery epoxy resin composition.

[0043]

[Table 1]

[0044]

[Table 2]

Using the powdery epoxy resin compositions of Examples and Comparative Examples thus obtained, semiconductor elements were transfer molded (conditions: 175 ° C. × 2 minutes, 175 ° C. ×).
After curing for 5 hours), a semiconductor device was obtained. This package is a 16-pin dual in-line package (DIP), and the semiconductor element is one in which aluminum wiring is formed on Si via an insulating film.

A PCBT test was conducted on the semiconductor device thus obtained. PCB test is 130 ℃
A bias voltage of 30 V was applied in a thermo-hygrostat of 85% RH, and the time for breaking the aluminum wiring was measured.

Further, by using the above powdery epoxy resin composition by transfer molding, a diameter of 50 mm and a thickness of 1 m.
A disk-shaped cured body sample of m was prepared, and the volume resistivity and the ion mobility were measured using the sample. The volume resistivity is 20
It was determined by the current value 1 minute after applying a voltage of 500 V at temperatures of 0 ° C. and 250 ° C. The ion mobility was obtained by the polarity reversal method. That is, after applying a voltage of 1000 V for 2 hours at a temperature of 250 ° C., the voltage polarity was reversed and the time (t) at which the current peak appeared was measured. Then, it is calculated from the following formula.

Ion mobility (μ) = d ² / t · V [In the above formula, d is the thickness of the sample (= 0.1 cm),
t is the time when the polarity is inverted and the current peak at that time appears, and V is the applied voltage (= 1000 V). ]

Further, the ionic impurity content of the above-mentioned disk-shaped cured body sample was measured. The ionic impurity content is
The crushed hardened body sample was extracted in pure water at 160 ° C. for 20 hours, and the extracted water was subjected to ionic impurities (Na ⁺ , Cl).
^-, Br ^-, it was detected by measuring by ion chromatography the content of SO ₄ ^2-).

The disconnection time of these aluminum wirings, the volume resistivity of the cured product sample, the ion mobility and the content of ionic impurities in the extracted water are shown in Tables 3 and 4 below.

[0051]

[Table 3]

[0052]

[Table 4]

From the results shown in Tables 3 and 4, the aluminum wiring of the comparative example product was broken within 40 hours, while the breaking of the aluminum wire of the example product did not occur for a long time. From this, it is understood that the product of Example has excellent moisture resistance reliability.

Claims (1)

[Claims] 1. A semiconductor element and a sealing resin layer for sealing the semiconductor element, wherein the sealing resin layer has the following characteristics (A) to
A semiconductor device comprising a cured body of a thermosetting resin composition having (C). (A) The thermosetting resin composition cured product has a volume resistivity of 5 × 10 ¹¹ Ω · cm or more at a temperature of 200 ° C. or a temperature of 250 ° C.
2 × 10 ¹⁰ Ω · cm or more. (B) The ion mobility of the thermosetting resin composition cured product is 1 × 10 ⁻⁸ cm ² / V · s or less at a temperature of 250 ° C. (C) The ionic impurity content of the extracted water of the thermosetting resin composition cured product at 160 ° C. for 20 hours is 100 ppm
Less than.